Smoke emitted from wildfires, peat fires and controlled burns on farming lands is associated with a yearly average of hundreds of thousands of deaths worldwide.

An international study which is the first to estimate a death toll for landscape fires revealed that they contributed to an average of 339,000 deaths per year between 1997 and 2006.

According to the report published in Environmental Health Perspectives, most of the deaths are concentrated in sub-Saharan Africa, where an estimated 157,000 people die as a result of being exposed to such fires annually.

Southeast Asia was the second hardest hit with 110,000 deaths annually, said Fay Johnston of the University of Tasmania, who represented a global team at the annual meeting of the American Association for the Advancement of Science (AAAS).

“I was surprised at our estimate being so high when you consider that the exposure to fire smoke is quite intermittent for most people,” Johnston added.

The study suggested a significant link between climate and fire mortality.

According to the findings, about twice as many people died during El Nino years when the surface ocean temperature rises in the tropical eastern Pacific Ocean (averaging 532,000) as during cooler La Nina years (averaging 262,000).

Although the toll from wildfire is far below deaths associated with indoor and urban air pollution, the new findings indicated that “fire emissions are an important contributor to global mortality.”

The previously estimated global toll for indoor air pollution was estimated to be at two million people per year and urban air pollution at 800,000.

Scientists suggested that the death rates could be reduced if people stopped burning tropical rainforests.